Process of making acetone.



No. 648,389. Patented Mav I. 1900.

H. 0. CHUTE.

` PROCESS 0F MAKING A CETUNE.

(Application led June 10, 1899.) (No Model.) 3 Sheds-Sheet I'.

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No. 648,389. Patented May-I, |900. H. 0. CHUTE.

PRDCESS 0F MAKING AGETDNE.

(Appliation led June 10, 1899.)

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No. 648,389. Patented May l, |900..

H. 0. CHUTE.

PBDCESS 0F MAKING AGETUNE.

(Application lud June 10, 1899.)

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UNITED STATES PATENT EEICE.

HARRY O. CHUTE, OF DESERONTO, CANADA.

PROCESS Vo| MAKING ACEToNE.

SPLECFICATION forming part of Letters Patent No. 648,389, dated May 1, 1900.

l Application filed June 10, 1899. Serial No. 720,087. (No specimens.)

To all whom t may concern.-

Be it known that I, HARRY O. CHUTE, a citizen of the United States, residing in Deseronto, Province of Ontario, Canada, have invented certain new and useful Improvements in Processes of Making Acetone; and I do hereby declare the following to'be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. f j

All methodsof making acetone from metallic acetates are based upon the fact that destructive distillation resolves the acetic radical into equal molecules of carbon dioxide and acetone. tion, which is caused by the tendency ot' some metallic acetates to give upa portion of their acetic acid bysimple volatilization upon heating, is usually oloviated,V by the expedient of making the salt basic to begin with by the addition of a small portion of a base, generally lime,4 (Handbuch der Chem., Liebig, Woehler du Poggendor, 1842, Vol. 2, page 1019.) Acetates so treated, when carefully distilled on a laboratory' scale, give a near approximation to the theoretical yield of acetone.

The fact that destructive distillation of metallic acetates yielded acetonepwas known in the last century, the reaction being carefully studied by Chenevix between 1803 and 1809, (GilbertsAnnaZen, 1809, Vol. 32, page 156.) The method he used was essentially the same as that now in use-viz., placing a portion of the salt in a retort provided with a condenser and slowly and carefully heating by means of external heat until the reaction was complete. On the large scale this process as at present conducted is unsatisfactory. It is discontinuous, requires much time, and any iuattention or carelessness results in large losses of acetone. As is said by an authority on the subject, Careful regulation of the heating within narrow limits of variation is far the most important velement in the process. Within very narrow limits, too little heat gives undecomposed acid, while too much gives in flammable gases instead of acetone. Slow and careful heating is enjoined by all familiar with the art, as the cardinal point in the process. Quick heating An inconvenient bye-reachas always been regarded as fatal to success; This idea, which was first stated by Chenevix,l have discovered to be an error. There is no reason whatever for prolonged heating of a particle of acetate. The reaction takes place only at a definite temperature, which, while differing with the different acetates, is constant for each and will take place when that point is reached, whether heating be rapid or slow. For barium acetate this critical temperature isbetween 400O and 405 centigrade. Foracetate of lime the tempera* ture is about 300 centigradel This tempera ture varies undercertain conditions, among which may be mentioned the vapor tension of the inclosure in which the lacetone is evolved. Hence the critical temperature can be'approximately stated only and under like conditions remains fixed or constant.

The error hasarisen from a misapprehension ofthe conditions of the process in common use. `It is not because long continued heating is necessary to cause the acetone making reaction to occur, but because if heat be toosharply applied to a mass of acetate lying ina retort local overheating occurs and acetone is lostin consequence. Acetone is decomposed when heated to a temperature not far above that at which it is formed, breaking up into tar, gas, and carbon. It also hasa tendency to polymerize at elevated temperatures, forming oily bodies ot' little value. The presence of the "free alkali usually initially added to the acetate and of the alkali carbonate formed by the reaction itself tends. to accelerate these detrimental byereactions.

Crystalline salts are bad conductors 01": heat, and when in the form of powders, as the acetate is in practice, their conductivity is even less. With a large bulk of such material (six hundred pounds is a common charge) lying in an externally-heated retort itis a matter of extreme diiiiculty to cause the mass to attain`the exact heat desirable to secure a maximum yield. lf a low heat approximating the reaction temperature be employed, heating of the entire mass takes place with intolerable slowness and the reaction is usually in- IOO complete, while it brisker tiring be used loss of acetone is likely to result. Portions of the salt lying next the wall become overheated 'yielding little or none themselves.

lIO

2 v I. V648,389'

and injure the acetone already formed, while c The use of a stirrer merely palliates the evil, since no large mass of the physical consistency of decomposing crude acetate can be stirred, so as to cause veach and every particle to acquire the desired temperature, neither more or less, with reasonable certainty.

' My'invention consists in substituting for this unscientific, wasteful, and tedious process of distillation in bulk a process of continuous destructivedistillation in transit,

treating the acetate in thin films, layers,

small consecutive qu'anti'ties,or in a finelydivided state either by passing it through a zone or over a surfacev heated to the exact .temperature required for conversion, simultaneously removing the acetone produced vfrom contact with the hot alkalineA mass.

This,I believe, represents vthe most impor'- tant step forward in the art of making'acetone since Chenevix. l

My process notv being dependent u ponany particular structure or apparatus,`a large variety of structuresmay be used to carryit ou t, such as ordinary'shaft and shelf furnaces and ldriers, in transit bone-black kilns and driers'. The only point is that the acetate be caused to travel forward .through'azone or over a surface of constant temperature in ak relatively-thin layer or finely-divided state,

l 'such heated surface of constant temperature being inclosedzto prevent' escape lof the acetone'and such inclosure being provided with meansfor` withdrawing the acetone as fast as formed. By this process sharp decomposition ofthe acetate isjobtain'ed and the acetone evolved lis at once removed to a relativelycoolerf place.

after speak more particularly of calciumk acetate, that being the salt generally used, and itbeing lunderstood that I regard it as'typical, sofar as my invention goes, of the ajceare also suitable; Excess of alkali in myl tetes of potash, soda, baryta, magnesia, zinc, lead, &c. f

In' detail I prefer lto proceed as follows: .The acetate is' made slightly alkaline vin the known manner to prevent loss of acetic acid. Lime is the most convenient base tofnse; but potash andvsoda and their carbonates may be used in lieu thereof. Baryta and strontia process doesnot have the detrimental edect that itfhas in theold process, since the acetone t does' not remain in contact with the hot mass,

, 'as it must do in the b ulk process, nor does 4mechanical means.

the mass become overheated. The powdered vacetate is fed from a suitable hopper into a chamberand `upon or in close contact with a heated surface kept at substantially the correct temperature, and over or past this s'urface itis caused to pass in a thin layer or in a'linely-divided'state by gravity or suitable lime. It is Vusually of-advantage to run the ing 'relatively -cooler chamber.

For the sake of convenience I shall herein-pA It at once breaks upv quantitatively into acetone and carbonate of feeding endrof the heated zone or surface at a temperature slightly lowerthanV the decomposing temperature of the acetate .to give an opportunity to drive off accidental moisture, dac., leaving conversion to take place at the point intermediate of the extreme temperatures. Bythis is'meant-that the receiving and the delivery end portions of the converting zone or surface vary from the critical `temperature'which is due, primarily, to locating the f urnac'e or heater at one end thereof, and which end is hottest,the intermediate portion being maintained at the critical temperature and the opposite o r receiving -end portion being of a tem peratnre lower than the critical point. The acetone expelled from this layer of material rises into thesurround- From this chamber it isremoved and conveyed to a condenser as fast as formed.

` It is a Well-known principle in chemical .physics that the liberation of a volatile body,

either by simple levaporation or by its direct formation, is accelerated by maintaining. its vapor tension at the point of formation as low as possible.- This, as is well understood,

may be done either by maintaining a vacuum at theplace of' formation or by constantly sweeping past a body of indifferent gas or vapor..` A familiarinstance of this is the 'formation ofquicklime. Limestone may be fused `withoutdecomposition ifv a moderate pressure of Vcarbonio acid be' maintained around it, while if a vacuum ismaintained .or if steamorair-is sent over it insufficient quantity vto sweep otf the carbonio acid as fast as formed decomposition takes place at comparatively-low temperature.. lThe more eicientthe removal of the carbonic'acid the more easily the reaction proceeds. A rlhe same .principle of course applies to making acetone,

and thereforeI runmy circulating-pump vconstantly and keep the chamber as free of acetone as may be. A vacuum maybe maintained or al current of "steam kept passing through. If steam is used, it has thesame v'advantageas other vapors or gases; butitvhas the disadvantage of `diluting'the condensed acetone. vA-ir cannot be used, since it would b urn the acetate andacetoneg: but any -oxygen-free gas may be. The point is simply to 'remove the acetone as fast as'possible by means of a current of. indiderent gas orivapor. 'I have found "that yby maintaining ka closed system and returning to the retort the incondensable gases passing the condenser in amount sufficient to maintain thedesired tension-is an efficient and economical way of proceeding'.

I' have deviseddifferent kinds of apparatus for carrying out the foregoing proce`ss,'of which the anneXeddrawin'gsillustrate-preferred forms.

Figure l is a detail View in elevation' of an apparatus for attaining the objects of this invention,"parts being brokenawayto show more clearly the relative arrangement of the IOO IIO

t substance over coperating elements. Fig. 2 is a transverse section of the chamber about on the line X X of Fig. 1. Fig. 3 is a longitudinal section of an apparatus of different form. Fig. et is a top plan view thereof. Fig; 5 is a view in elevation of still another form of apparatus for effecting the objects in view, parts being broken away. Fig. 6 is a transverse section thereof about on the line Y Y of Fig. 5.

Corresponding and like parts are referred to in the following description and indicated in all the views of the drawings by the same reference characters. ln the form shown in Fig. 1 the chamber in which the destructive distillation of the acetate is carried on is arranged at an'inclination, so as to take advantage of the force of gravity as an active agent in feeding the the heated surface and through the heated zone in which the evolution of the acetone takes place. This chamber 1 is closed, so as to prevent the escape of the vapors when evolved or generated. The lower wall 2 of the chamber is fiat and straight, whereas the top and sides unitedly are of arch form. The acetate is supplied to the chamber at its upper end, being fed thereto in relatively small or minute quantities in consecutive order, whereby the salt spreads in a relatively-thin film or layer or becomes nely divided, so as to insure a rapid heating thereof and a quick evolution of the ace'- tone. In order to insure a positive feed of the salt over the lower wall 2 ofthe chamber, thereby preventing caking or sticking of the substance,'it has been found expedient tov combine with the chamber a force feeder or conveyer, the same consisting of an endless belt 3, provided at intervals in its length with blades or wings 4, which sweep over the surface of the lower wall 2 and carry the substance throughout the extent of the chamber and maintain the heating-surface in prime condition. This endless conveyer is supported at its ends upon rotary supports 5 and 6, which may be sprocket drums or pulleys, one ofthe supportsconstituting the driverand having the propelling force applied thereto.

The hopper 7, located at the receiving end of the chamber, has connection therewith by a neck portion 8, which is provided with a swelled or approximately-circular portion 9, in which is rotatably mounted a feeder 10, the latter consisting of a drum provided in its surface with a series of pockets, channels, or cavities', in which the acetate is received as the said pockets successively register with the receiving end of the neck 8, said acetate being discharged as the pockets aline with the lower end of the neck in the rotation of the feeder. It will thus be seen that the acetate is fed in relatively small or minute quantities inf-consecutive order so long as the apparatus is in running condition. The feeder is actuatedin any desired manner and, as shown, is driven by means of a belt 11, connectin g the pulley on its shaft with la corresponding pulley on the shaft of the upper rotary support 9, to which the power is applied for operating the endless conveyer.

The discharge at the lower end of the chamber is controlled by a valve or cut-off 12, which is opened at stated :intervals to admit of the accumulated waste carbonate escaping. A receptacle 13 is in communication with the discharge-outlet and is separated therefrom by the cutso or valve 12. A second cut-off or valve 14 is provided at the lower end of the receptacle 13 and is closed when the cut-off or gate 12 is open, thereby preventing the escape of gases and vapors should the same find an uninterrupted passage. A box 15 is located opposite the discharge-pipe 16, and its outer or front wall is upwardly and outwardly divergent, forming a chute to facilitate the shovelin g away of the waste product resulting from the process of distillation. When the gate or cut-oif 14 is closed, the cutolf 12 is open and the residuum passes from the chamber 1 into the receptacle `13, and when the latter is filled the cutoff 1.2 is closed and the gate 14: opened, thereby permitting the waste to escape into the box 15, from which it is removed to a convenientrpoint of deposit.

The lower wall 2 of the chamber 1 constitutes the heating-surface over which the acetate is passed and in practice will be heated to the required temperature in the most con-V venient manner, and, as shown, afurnace 17 is located at the lower end of the chamber, and its upper portion comes beneath the wall IOL 2 and inclines therewith, said wall '2 being common to the chamber 1 and combustionchamber of the furnace 17. The side walls of the combustion-chamber 18 curve inwardly at their upper ends, as shown most clearly in Fig. 2, and join with the side walls of the chamber 1 about in the plane of the wall 2, thereby leaving the upper portion of the chamber'l exposed to the cooling influence of the surrounding atmosphere, which is of advantage in preventing overheating of the actono when evolved in the process of distillation. The chamber 1 has its walls of plate metal, whereas the walls of the furnace and combustion-chamber are of masonry,with the exception of the wall 2, which is common to the chambers 1 and 18. A stack 19 has connection with the upper end of the combustion-chamber 1S and carries off the products of combustion. As a result of having the IlO furnace located at one end of the chamber 1 sponds to the exact temperature at which the` acetone is evolved from the acetate.

The acetone when liberated is in the form of a vapor or gas and is converted into available form by means of a condenser, the latf y for carrying off the acetone immediately upon i n v 648,3@

ter-forming' an'essential part of' the appara-- tus and being connected with the upper portion or Wall of the chamber 1 by means of a pipe 2O and dome 21. The condenser 22 may be of any form `or variety so long asit will subserve the purpose of reducing the vapor into liquid form. The discharge 23 of the f measure are separated from the acetone by meansof thje condenser` andare returned to the chamber to be used again as a medium its 'liberation from the acetate. These gases are saturated with acetone at thetempera-vl lture at which they leave the condenser.

By returning these to the retort` and 4again runv ning themV through the condenser this loss of acetone is prevented. A fan or 'steam-jet -z'le-to dip therein to a vblower 26 isthe means employed for positively circulating this gas or medium through the chamber l and condenser and is connected With the discharge 23 by means of a'pipe 27,A

a corresponding-pipe 28 connecting said fanblower Withtheupper portion of the lower terminal of the chamber'l. A valve 29 is located in the-length v'of the pipe 28 to shut olf the current or blast When'desired. Inasmuch as 'foreign gases are continuously generated in the operation of the-apparatus means must 'be provided for the escape of thesurplus amount4 and yet collect any free-acetone not reduced by thecondenser. vT-heescape ,forl

theexcess of vapor and-gases consists of a liquid-sealed outlet which, as shown, com- I prises a nozzle 30 and a cup 31,7the latterc'on-y taining ay liquid into which the discharge end n of thenozzle dips.' By varying the level of the liquid in the cup 31, so as to cause the nozbe varied.A It is presumed that the quantity of liquid in the cup will remain'constant, and in order vto change the eective` level of the liquid said cup is moved vertically with reference to the nozzle and any desired means maybe resorted tolfor supporting the cup at Y the'required elevation, and, as shown, a jack 32 of ordinaryv construction is provided as a simple and effective means for attaining the desired end, although it is to be understood that the jack may be replaced by a variable support vof anynatu re. The acetate orbasic salt is placed in bulk in thehopper 7, and the endless conveyer and feeder being set in operation the acetate is fed into the chamber 1 in relatively small or minute quantities in consecutive order and becomes spread upon the wall or heating-surface 2 and advances by gravit-ation or by the combinedactionof gravity and the endless conveyer 3. As the acetate reaches the middle portion of the heated surface 2 conversion takes place and the acetone is evolved in the form of vapor,Whichis-imme greater or less extent, the -pressure of the circulating medium can diately carried @if by the circulatinginedini or current of oxygen-free gas passing through the chamber 1, incident to the operation of the fan-blower. The acetone in the form of vapor passes to the condenser'and is reduced to available or liquid form and escapes into the receptacle 25. The process is practically continuous' and uninterrupted,- since the acetate is fed without interruption as lon g as the apparatus isin running condition; The Waste carbonate continuously discharges at the lower end of the chamber. It Will thus be' .seen that there is a continuous feed of the salt, a continuous discharge ofthe waste car- -b'onate, and a continuous outcw of theacetone, 'the several operations being effected at one and the sametimeand practically in suc= cessive order.

In thexform of apparatus shown inV Figs. 3 y

and4 the'feeder, condenser,'fan-blower, trapoutlet for the liquid acetone, and the regulator for the escape of the surplus circulating medium are-omittedfsince they'are substantially the same as shown and described in connection V-with the vform illustrated lin Fig. `1. This is also true of the form ofapparatus showninFigs. 5 and 6.. The chiefdierence exists in the construction ofthe chamber,

the furnace, and the means for eifecting a positive feed of the acetate'over thev heated ysurface andi causing a spread of thesame, so

as to insure every; particle being brought into f contact with the heated 'surface,so as toe'fn fecit a liberation of thea'ceton'e. -In the form shown in Figs. 3 and 'et-the heatj ing-surface 33 is a metallic plateof vcircular outline surmounting a combustion-chamber 34'of spiral formation' and connectedl at its vouter end-'with a furnace 35 and at its-inner IOO end with afstack 36. Thevshell or casing 37 inclosing the chamber in which the ,destructive'distillation is carried on is approximately of dome shape andl isv preferably of metal. The acetate is fed upon the center portion of the `heating-surface 33 by vmeans of a spout 38, connected with the hopper` 7, with which coperates the feeder 10 in the manner herein set forth. Thel central lportion'of the heating-surface 33'being connected with the stack or outlet 36 is cooler'than the outer portion, which is in direct contact with` the flame and gases from the furnace 35. Theintermediate portion of the heating-surface 33v is of mean temperaturev corresponding to that required for the evolution of the acetone.- Positive means are essential lto effect a distribution of the acetate over the heating-surface and cause it to move `fr om the center out- Ward to the discharge 39. As shown, the feeder consists of a kd'iametrically-disposed sweep 40, provided at intervals in its length with blades 41, connected by spring-arms 42 with thev sweep, said blades being disposed obliquely tothe radiiof the axial line of rotation of the feeder. A leveler 43, consisting of agbar, is disposed to operate immediately in the rear of the blades 41, so as to IIO spread the acetate over the heating-surface 33 after the action of the blades 41 in effecting the outward movement thereof. The acetate is deposited upon the central portion of the heating-surface and'is immediately' acted upon by the innermost'blades and moved outward, the leveler serving to spread the acetate in its new position. The blade following the one previously acting upon the substance comes in contact therewith and moves the same outwarda distance corresponding to its width, and all the blades in succession act upon the acetate and move it from the center to the point of discharge 39, as will be readily understood. The outward movement of the acetate is progressive, depending upon the extent of the blades 4l and the rapidity ofthe feeder.v The leveler and sweep are attached to the lower end of a vertically-disposed shaft 44, which is driven by any suitable source of power` by means of the intermeshing of mitergears 45.

In the form shown in Figs. 5 and 6 the chainber 46 is of circular outline in transverse section and is disposed horizontally and is located over the furnace and combustion-chamber 4:7 of substantially the same form as that shown in Fig. 1, the furnace being at one end and the stack at the opposite end. The conveyer48 is of the screw type and feeds theA acetate through the chamber continuously and at the same time serves to distribute and agitate it, so as to bring every particle into contact with the heating-surface. As in the previously-described forms, the chamber 46 has its lower portion only in contacty with the heating medium, the upper portion being exposed to the cooling in tluence of the air, whereby overheating of the acetone is avoided. The discharge-pipe 16 extends into the box `15, the cut-offs being dispensed with, since care is to be observed in removing the waste, so as not to entirely uncover the delivery end of the discharge 16,-whereby advantage is taken of forming a seal to preventthe escape of the acetone by means of the waste residuum.

It is to be expressly understood that the apparatus is subsidiary to the vital feature of the invention, which resides in the process of treating metallic acetates to effect a separation of the acetone by destructive distillation, said process having for its fundamental principle the evolving of acetone from an acetate by subjecting the latter in a finely-divided state or relatively-minute quantities in successive order to a heating medium of the exact or required temperature to liberate the acetone without resolving it into undesirable substances or products such as result from overheating and at the same time carrying oif the acetone and preventing its injurious contact with the hot mass of resultant Waste carbonate.

I have also discovered that my process of destructive distillation in transit is equally `resorted to.

`simple or mixed, are substances of higher boiling-point, this increasing as the scale is ascended. They are also more sensitive to heat, breaking up with more rapidity. For this reason my improved process of distillation in transit yields more important advantages, even With these more complex bodies, than it does with acetone itself. With the higher bodies the features of diminishing the y Vapor tension is particularly important, and in most cases the use of vacuum should be Using vacuum and transit distillationv from stearic-acid salts am uch larger proportion of stearone can be obtained than is possible in distilling in a retort, in which case the bulk of the products is decomposition products. Various acids of the aromatic series, suchas benzoic acid, when converted into salts and distilled with fatty-acid salts yield mixed aromatic aliphatic ketones. From the foregoing it will be readily understood that the manufacture of such higher simple and mixed ketones fromv metallic salts of organic acids by destructive distillation in transit is regarded as within the purview of the invention as set forth in the appended claims. f

Having thus described the invention, what is claimed as new is 1. The manufacture of ketones from metallic salts of organic acids, which consists in subjecting a progressively-moving thin iilm or layer of suchsalt to the action of heat sufcient for the formation ofa ketone, substantially as described.

2. The herein-described process of obtaining acetone from `acetates which consists in passing the pulverulent material in the form of a thin film or layer over a heated surface maintained at substantially the temperature set forth.

3. The herein-described'process of obtain ing acetone from acetates which consists in passing the pulverulent material in the form of a thin film or layer over a heated surface maintained at substantially the temperature set forth and removing the solid residuum as fast as formed.

fi. The herein-described process of obtain-4 ing acetone from acetates which consists in passing the pulverulent material in the form of a thin ilm or layer over a heated surface maintained at substantially the temperature set forth and removing the acetone as fast IOO vapor.'

5. The'herein-described process of forming acetone, consisting of passing the acetate in a relatively-thin layer or finely-divided state over a surface heated to the proper degree ot' temperature to insure `rapid conversion and an evolution of the acetone and simultaneously and continuously reducing the tension of the acetone vapor to the smallest amount possible, substantially as described.

ing acetone, consisting of bringing lthe ace'- 6. The herein-described process of productate ina finely-divided state into contact with a surface heated to the proper temperature for effecting conversion, and simultaneously removing the acetone from the hot alkaline mass by a current of oxygen-free gas passing immediately over said surface in direct contact with the mass at the point of evolution, substantially as described.V

7. The herein-described process of producing acetone, consisting of continuouslypassing the acetate in, a relatively-thinl layer or,l

finely-*divided state over a surface heated suficiently to liberate the acetone, and passing a current of oxygen-free gas over the hotalkalinelnass-and advancing acetatein anv inverse direction to fthe movement of the ace-v tate, substantially as described.

8; In the production of acetone by the 'de-v structive distillation of a. metallic acetate,

' y passing the latter through a zone having a ing theacetonefroinl the heated alkali and sweepingit past the acetate 'inversely to its mean Vtemperature correspondingtothat nec,-

essary to evolve the acetone, instantlyseparatadvance movement, substantially asset forth.Y 9. In the process of producing acetone by tlie destructive distillation of an acetate, supplying the acetate in 4minute or relativelysmall quantities in successive-order to a properly-heated surface, separatin g the .acetone from the evolved gases,and again utilizing the latter in the continuous operation of the process, substantially as set forth.

10. .Iu'the process of'prod ucing acetone by the destructive distillation of an acetate, spl plyin g the acetate in minute orrelatifvely-small quantities in successive order to a properlyheated surface, passing a gaseous current over the'salt to carry off the acetone when liberated', separating the acetone from the gaseous carrier, reheatingthe latter and again passing stantially as set forth.

11. In the process of producing acetone by the destructive distillation of an acetate, sup- Vsufficient to evolve the acetone, passing a current of indifferent gas over the salt to carry oit the acetone, separatingthe acetone from the indifferent gas, reheating the latter and again passing it over the acetate.

13. In the process, of evolving acetone from an acetate at the critical temperature, reducing the vapor tension simultaneously with and atrthe point of conversion of the salt, substantially as set forth. Y

14. In the process vof evolving acetonefrom acetate subjecting the salt in transit in a film .or relatively-small vquantities in consecutive `of aliphatic organic acids Yin a progressivelymovingA ilm or layer to the action of heat maintained at the critical temperature, substantially as described.

`tothe-action of' heat maintained at the critical temperature, substantially as specified. v. In testimony whereof I affix my signature `in presence of two witnesses.

HARRY 0.

` Witnesses: v

0. C. HINES, GEO. E. FRECH.

CHUTE.. [L s] vas formed; by a current of indifferent gas or it over the acetate for usc in the mannersub- IOO 

